You can buy a peep hole thing for a door,at a hardware store. And then use it backwards so when you look at your quilt block it looks far away. This is an excellent way of seeing if the colors you are using have enough contrast. They sell the same thing in quilt shops under a fancy name. Don't know if this is what you are thinking about.

The mirrors, while they can do the same thing, are generally used for seeing how repeats (S&W, OBW) will look when made into a block.http://www.amazon.com/Quilting-Quilt.../dp/B001UAF6JO
You can also get them custom made at your local Lucite or glass dealer. I did this for 2 quilts I made where the smaller mirrors just weren't showing me enough.

The mirrors, while they can do the same thing, are generally used for seeing how repeats (S&W, OBW) will look when made into a block.http://www.amazon.com/Quilting-Quilt.../dp/B001UAF6JO
You can also get them custom made at your local Lucite or glass dealer. I did this for 2 quilts I made where the smaller mirrors just weren't showing me enough.

I have the little gizmo that MTS has mentioned ... just hold it to your eye and you see several of the same block. However, my eyes have not masted the "how to" of it!!

The OBW etc mirrors ... I purchased two mirrors at the $ $tore, taped them together so I can stand them on end. Then just move them til I see 4, 6 or 8 reflections. I even keep them in my truck, ready at a moment's notice, just in case I see some potential fabric I need to check for it's OBW'ability! :)